A SEEMINGLY innocent stumble while getting ready for work one day took Keith Swankie by surprise. He had no idea it would signal the start of a gruelling battle that would rob him of his health, his independence and, one day, his life.

The former Morrisons deputy store manager suffers from progressive supranuclear palsy, a terminal condition which kills off the nerve cells in the brain, affecting balance, movement, vision, speech and swallowing.

Caused by the over-production of a protein called tau in the brain, it’s a rare illness that affects about 4000 people in the UK.

At just 43, and with a wife and two young daughters, Keith and his family, of Arbroath, Angus, are facing up to the reality that he probably won’t see his 50th birthday.

PSP will continue to eat away at his healthy brain cells until he is no longer able to move, eat, speak or open his eyes.

He said: “It has sunk in now that I will eventually die, but in the latter stages I won’t know what’s going on, I’ll just be existing. Imagining how that will feel for my family is so hard. I can only pray it won’t last too long.

“Every single day I make sure I tell my wife and our girls how much I love them, because I know I’ll wake up one day and I’ll no longer be able to.

“Sheelagh and the girls are staying strong for me and I can’t let them down. I can’t stop this disease but I won’t let it beat me.

“While I’m still able, I want to make as many people as possible aware of PSP. I have to carry a card saying what’s wrong with me because even some paramedics and hospital consultants aren’t very aware of the condition and that has to change.”

Diagnosis of PSP is difficult because symptoms mimic other conditions including multiple sclerosis and Parkinson’s disease.Keith’s first fall was in August 2009 and, by March 2010, he couldn’t get about without a walking aid. His condition was finally diagnosed in April 2012.

Average life expectancy from the onset of the condition is seven years. It is now five since Keith’s first symptoms and his wife, mental health worker Sheelagh, 42, and daughters Nikki, 20, and Jordan, 16, can only guess how much time he has left.

His deterioration in the past year has been rapid. The muscles in his eyelids are affected and his eyes stay clamped shut for 80 per cent of the time. He has severe difficulty walking, suffers some incontinence and lives in fear of choking while eating because his swallowing reflex is affected.

Keith said: “Most of all, I feel I’ve been robbed of the chance to grow old with Sheila and see my girls have families of their own.

“If they get married, I won’t be there to walk them down the aisle. If they have kids, I’ll never get to hear them call me grandad.

“Those are the things that get to me in my darker moments.”

The family have made a video for the PSP Association to raise awareness and funds for research.